Conductivity and microstructural evaluation of SGDC solid electrolytes synthetized by Pechini and controlled precipitation

Abstract

In this work, controlled precipitation synthesis methods and polymeric precursors (Pechini) were used to obtain gadolinium-doped cerium oxide solid electrolytes (Ce0.8Gd0.2O1.9) and double-doped cerium oxide with gadolinium and samarium (Ce0.8Gd0.2−xSmxO1.9x=0.01; 0.03 and 0.05). The main results indicate that the synthesized powders by the Pechini method present better microstructural characteristics such as larger specific surface area and smaller particle size. Test specimens were compacted (187MPa) and sintered (1500°C/6h) and subsequently characterized. Through the impedance spectroscopy analysis, an increase in the percentage of the samaria caused an increase in the grain boundary and grain conductivity in all the samples under study. In the grain interior, samples without samaria showed heterogeneous regions, where the cation-vacancy pairs are tightly bound, precluding these vacancies from participating in ion conduction. In the samples with samaria, these defect groups are smaller, indicating structural homogeneity, resulting in greater ionic conductivity. Grain boundary specific conductivities show slight increase for samples codoped with samarium oxide. This effect suggests that Sm3+ additions change the charge equilibrium in space-charge layer favoring better dopant distribution.